The invention relates to the field of automatic bursting of perforated continuous forms. More particularly, the invention relates to modular apparatus for bursting forms which includes dual speed rollers and a bursting blade to accomplish form separation, and paper guiding, trimming and stacking means.
The growth of modern high speed data processing and printing has led to the use of continuous web materials as printing media. Generally, whether they take the form of invoices, paychecks, ledger sheets, or the like, such forms come in a variety of sizes. Most modern forms have margins containing sprocket holes for use with the well known tractor pins drive used on high speed data printing equipment. Most forms also include pre-weakened areas or perforations which allow the forms to be readily separated from one another. In addition, many uses of such forms require the generation of one or more copies, and continuous forms are often provided with manifold sets of carbons and copy layers.
However, with the increased utilization of such continuous forms, a concomitant increase in the need for simple and reliable automatic bursting apparatus has been felt. However, up until now, most such units were noisy, bulky, mechanically complex, have required time consuming adjustments for changing from sizes, and were prone to troublesome jamming or misregistration of the forms, thus causing great delay in processing of the forms.
Well known prior art devices commonly use a pair of high speed rollers and a pair of low speed rollers coacting with a bursting blade to cause separation along the preweakened zones of suitable continuous forms. Generally, the forms would be guided to the bursting unit by a pair of mechanically complex tractor pin drives which were adapted to engage sprocket holes provided along the margins of the forms. Such prior art guiding means suffer from the obvious disadvantage that only forms provided with standard sprocketed margins can be used in the machine. Before passing on to the bursting unit these sprocketed margins would generally be removed by a pair of dual rotating trimmer blades disposed in the forms path. Thus, before being burst, prior art devices require that both the tractor pin guides and the trim cutter units, which ride on transverse guide rods, be exactly aligned. Especially critical is the alignment of the tractor pin guides which, if not properly aligned, or securely locked onto their transverse guide rods, will cause the forms to be skewed, resulting in the forms being crumpled, improperly burst, or even torn. Prior art devices have attempted to overcome these problems by providing positive locking and stop means for the paper guides and trimmer units. These positive locking means usually have taken the form of some sort of thumbscrew, or lever operated camming device to lock the trimming and guiding units in place along a transverse guide rod. However, in order to prevent side to side play while forms are being fed into the machine, small stop blocks, also operated by thumbscrew or lever operated camming devices have been employed. Thus to load a form into prior art devices, an operator must first loosen a set screw or release a locking device on both the tractor pin units and their respective stop blocks, precisely align the tractor pin unit up with the sprocket holes of the forms, and relock or refasten all the above elements. The same sequence of steps of unlocking, resetting, alignment, and relocking must be followed for the trimmer units, which steps often present a hazard to the operator since the locking mechanism on the trimmer units is often quite close to the sharp blades of the trimmers.
In well known prior art devices the trimmed forms then continue on to a pair of fixed low speed rollers, having a bursting bar disposed thereon, and thence to a pair of movable high speed rollers. Generally, the high speed rollers are supported by a toothed track arrangement. This arrangement necessitates forming the tracked portions in heavy side plates which can withstand the high stresses generated during the bursting operation. However, such an arrangement necessitates the use of heavy materials and a bulky structure of stamped metal side plates to house the fixed low speed rollers and the movable high speed rollers. Additionally since all the load bearing stresses are present in the side plates a high degree of undesirable mechanical noise is present whenever a form is being burst. Furthermore, if a shingling stacker is desired, it must be attached securely to the movable high speed end for movement therewith, which results in an undesirable increase in the mechanical complexity of the unit and also makes it more difficult for the operator to adjust for different size forms since greater mechanical force is required to simultaneously move the high speed roller unit and the shingling stacker. Even those prior art bursting devices which have movable low speed rollers and fixed high speed rollers have used the above mentioned stamped metal side plates and toothed track arrangement to support and adjustably separate the high and low speed rollers. Additionally, prior art bursters make little provision for properly guiding the forms once they enter the bursting section. Generally a flat bed or platen is provided between the low speed and high speed rollers, with pressure rollers or wheels which are used to help keep the forms skewing or misregistering. However, such techniques are subject to undesirable aerodynamic problems in that thin forms often will not properly glide across the bed under the rollers and therefore be skewed, improperly burst, or jam the bursting apparatus. Additionally, such guiding means is bulky and expensive to manufacture.